Sensors and analyzers suitable for detecting trace amounts of explosives, narcotics and other vapors of interest require calibration from time to time. Typically, these analytical devices are calibrated by measuring a controlled amount of the desired compound produced by a vapor generator. Currently available vapor generators operate by injecting a controlled amount of analyte into a stream of clean gas. In practice, the gas stream passes over a temperature controlled bed of analyte. The temperature of the bed is selected to continuously evolve a controlled amount of analyte into the passing gas stream. Thus, these systems are capable of accurately producing gas streams containing minute amounts of nearly any analyte.
Unfortunately, currently available systems have several limiting characteristics which preclude their use in the field environment. The requirement of a clean gas stream necessitates the use of a filter system or compressed bottled gas. Additionally, current vapor generators rely on precision pumps and flow meters to ensure an accurate and controlled gas flow rate. Finally, the operator must precisely control the analyte bed temperature to insure uniform evolution of the analyte into the flowing gas. As a result of these limitations, currently available vapor generation systems are complex, bulky, power hungry and expensive devices unsuitable for use in the field.